Electrical measuring device.



C.LE G.FORTESCUB ELECTRICAL MEASURING DEVICE.

APPLICATION FILED OCT. 31. I913.

1 1 86,76 5 Patented June 13, 1916.

WITNESSES: INVENTOR J ATTORNEY UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESOUE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

Application filed October 31, 1913.

To all whom it may concern:

Be it known that I, CHARLns Ln G. Foa rns- Con, a subject of the King of Great Britain, and a resident of l'ittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electrical Measuring Devices, of which the following is a specification.

My invention relates to electrical measuring systems and particularly to methods of measuring voltages.

The object of my invention is to provide a method of measuring the maximum value of the voltage of a circuit.

Various methods have been proposed for measuring hightension voltages, the most usual methods being to measure the lowtension voltage of a main transformer and to multiply this value bythe ratiooi' transformation, to use a voltage transformer and to use an electrostatic voltmeter. The first method gives results very much in error, on account of the distributed. capacity in the high-tension winding of the transformer, harmonic distortions of the applied voltage wave, and the capacity ol' the terminal. bushings and the apparatus to which the high-voltage winding is connectedv Furthermore, unless the wave is a pure sine wave there is no method of getting the maximum voltage. The second method an improvement over, the first method but requires corrections in most cases and is expensive because it requires the use of another transformer. The third method corrects the reactive errors of the ratio method but gives also an elfective reading and does not indicate the wave shape or the maximum value of the voltage.

Recently, sphere gaps have been proposed for the measurement of high voltage on account of the fact that the rupture of a given sphere gap is independent of frequency and of time of voltage application, and that it depends only upon the maximum value 51' the ,improssed voltage provided there is no ionization before the air breaks down and there is no corona at the surface of the spheres. As a sphere gap will not indicate the voltage of a circuit below a definite maximum value, I have provided a method of indicating the Specification of Letters Patent.

Patented June 13, 1916.

Serial No. 798,529.

maximum value of the voltage at any time, irrespective of any change in the shape of the voltage wave. My invention may be used however, to calibrate a sphere gap for operation at definite maximum voltages.

The single figure of the accompanying drawing is a diagrammatic view of an electrical circuit used in caliln-ating a sphere gap by a method embodying my invention.

In order to determine the maximum value of the voltage of a circuit 1, I provide means for measuring the average value of the voltage drop across a non-inductive resistor 2 through which transmitted the charging current of a condenser 23 that is connected across the conductors of the circuit 1, the voltage of which is to be measured. 1 provide an auxiliary circuit 4 comprising resistors 5, a galvanometer 6 and a contact making and breaking device 7 for determining the average value of the potential drop across the resistor which is proportional to the condenser current. I pro ide also a circuit S which is connected in shunt across the resistor 2, comprising a switch 9, a battery 10 and a potentiometer 11 which is used to calibrate the galvanoinetcr (5.

One application to which my method may be applied, as hereinafter stated, is to calibrate a sphere gap 12, for which 1 provide a generator 13 supplying current to an auto testing trz'tnsformer 14, a voltmeter 15, a choke coil 10, damping resistor 17 and a control resistor 18.

The condenser 3, as shown, is an air condenser and is constructed of Wood arefully turned to dimensions and coated with tin f il and lead sheeting. The central highvoltage member 19 is suspended within three sections 20, .21 and 22, the outer two of which are connected together and connected to ground through a resistor 23. The central member 21 is connected through the re sistor 2 to ground, as is terminal 2% of the sphere gap 12 and terminal 25 of the transformer 14.

\Vhen the voltage is impressed across the sphere gap 12, the condenser 3 Will take a quantity of electricity to charge it which is proportional to the maximum value of the impressed voltage and the capacity of the condenser, and, since the quantity of chi-o tricity is proportional to the time and current, the following formula is correct for Waves having odd harmonics.

1:4(JVF where I average value of the condenser current.

C capacity of the condenser. I" frequent} of the voltage wave. V niannnuin voltage.

. if V loin The constant ll: of the galvainnncter ma; he read from a calihraiion chart, ii a different for various deflections of tin gaivanometer, but, in order to drtern e the constant 7: when it remains the same for vari ous deflections of the galvauoineter. the switch 9 is closed and the contact device 7 started, and, for various values of the voltage impressed across the resistor measured by the potcntionn-ter ll, the delc-i-i'ion (d) is noted. The potential drop ac the resistor 2 is proportional to the av value of the current and the constant the number of divisions of deflection {(f) per ampere. it must he borne in mind that the galvanomcter r aiding will he only one half the valueof the potentiometer reading, since the contact device 7 is arranged l'or either short-circuiting the galvanoiucter every alternate half cycle, or for removing the galvanometcr from the circuit every alternate half cycle, and is driven hy some form of motor (not shown). However, the galvanometer ma be reversed ever; halt cycle by the device 7, in which case it will indicate the same values as the potentiometer. The brushes 26 are so adjusted as to operate at the correct point on the voltage Wave.

The outer plates of the condenser are connerted to resistors so adjusted that the time constants of the center and ends of the co h FS-H' will be approximately the same, and, since the parts are all grounded, there will be no leakage from one section to the other.

inset ea M 40KB the deflection is noted and, sinceily oi" the coiulcnser, the frequency of the volt: |gn= wave and the coin-taut of the gal \azuunrter have been deterniinmi previously,

the nia:\..;n;uni voltage may he calculated dithe capachaic Sci forth a method of measinaxnnurn \alue or the voltage hunting a splnprc q", my invennig lllr', maximay; ma, n:-

r wl i'or nniasui rlu: iwiiltage for anv other pur- :hlllhtle, of rrgulating the device and Yufin s in of con- 7 er may he used within the win; of the apyein'lwl clainm l l v 212M521 Kaine Jl pose.

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l q '1 r l. A zr r the maximum value cl 3 H lure wave minor mug! moans for cl on-9 he voltage t we n-raw; and mean for determining the mean why, 1 t urrcnt otwill irmnicnwr iiltilYiilS, of time E2. A method ol measuring the maximum value oi a \iutag c wave w nshtinu' in first cliaigi a coinlensrr with the vm" to he lllt'llr llu ii {hm e value of the f llhltlilw r l hall cycle (it the aw and the!) computing iu'. maninz nn value unlxage. lrnoning the cu- ])n i T xuriucr and the frequency A i1" 5 r meaeurinn' the maximum value of a voltage wave consisting. first of charging a coiuleniser iron! the circuit the voltage wl' which in to he measured then sending the charging current tliirougrh a resistor, til measuring the deflection oi a gal- -';l1'u)lil(t'-}, saic galvanonwterbeing connected in shunt to the said resistor and computing the inaniniuni \alue of the voltage, knowing the capacity oi the condenser, the frequency of the circuit, and the deflection coustaim; oi the alvainnneler.

4. Av method of commuting the maximum value of a voltage wave consisting in first charging a coinlenser with the voltage to he lilczh uflfti. then measuri In; the average value of the conden er curnazh and then computing; the minimum urine of the voltage, knowing the capacity of the condenser and the fr rquency of the wave.

5. A method of measuring the maxin'iuni value of a voltage wave consisting in connecting a condenser across the circuit the maximum value of the voltage wave of which is to be measured, then sending the charging current through a resistor, then connecting a galvanometer across said re sistor and short circuiting the current from the galvanometer, except every alternate hall cycle, then computing the maximum value of the voltage wave, knowing that said maximum value of the voltage wave is directly proportional to the deflection of the galvanometer and inversely proportional to the capacity of the condenser, the frequency of the voltage wave, the constant of the galvanometer in divisions per ampere and a constant four.

6. A device for measuring the maximum value of the voltage of a circuit comprising a comlcnser connected across the circuit, a resistor in series with the condenser, a gal- Ymuuncier in shunt relation to the resistor and means connected between the galvanometcr and the resistor for short circuiting the id galvanometer under predetermined col'nlitiuns.

7. A device for measuring the maximum saiue of the voltage of a circuit comprising a (:(nnl'cnser connected across the circuit, a resistor in series with the condenser, a galvaulnimter in shunt relation to the resistor and n ns connected between the galvanun and the resistor for rectifying the current Lhat traverses the galvanometer.

5 device for determining the voltage at an rh-ctric circuit comprising a condenser m-ni-iczccl across the said circuit and means 1- detcrmining the value of the charging.

-e circuit.

c5 measuring the maxiu, voltage wave consisting in he voltage wave, knowing charging a condenser with the voltage to be measured, then measuring the average value of the condenser current and then computing the maximum valueof the voltage, knowing the capacity of the condenser and the frequency of the wave.

11. The method of measuring the maximum value of a voltage Wave consisting in charging a condenser from the c' cuit the voltage of which is to be measu ed, then sending the charging current through a resistor, then measuring the deflection of a galvanometer that is connected in shunt relation to the resistor and computing the maximum value of the voltage.

12. The method of measuring the maximum value of a voltage wave consisting in charging a condenser with the voltage to be measured, then measuring the mean value of the charging current of the condenser. 13.'A voltage-measuring device comprismg a condenser that is supplied with current proportional to the voltage to be measured, a measuring instrument and means connected between the measuring instrument and the condenser for rectifying the current that traverses the measuring instrument.

14. A voltage-measuring device comprising a condenser that is supplied with current proportional to the voltage to be measured, an electro-responsive device connected to the said condenser and means for rectifying the current that traverses the electroresponsive device.

15. A device for measuring the maximum value of a voltage Wave comprising a condenser supplied with current proportional to the voltage to be measured, a galvanometer and a rectifier connected between the galvanometer and the condenser.

In testimony whereof, I have hereunto subscribed my name this 22nd day of Oct. 1913.

CHARLES LE G. FORTESCUE.

Witnesses:

WALTER M. DANN, B. B. HINES. 

